Blends of certain EP or EPDM polymers with crystalline polypropylene (optionally containing up to about 10% of another .alpha.-olefin) are disclosed in U.S. Pat. No. 4,036,912. U.S. Pat. No. 3,515,775 describes three component blends of (1) an amorphous EP or EPDM polymer, (2) crystalline polypropylene (including polyallomers or copolymers of propylene), and (3) crystalline polyethylene. U.S. Pat. No. 3,632,674 discloses three component blends comprising (1) a crystalline EP block copolymer, (2) crystalline polypropylene (optionally containing up to about 10% of another .alpha.-olefin, and (3) an ethylene polymer or statistical copolymer of ethylene containing not more than 10 wt. % of an .alpha.-olefin. Each of these references teaches propylene homo-and copolymers as essentially interchangeable in the blends described therein.
Past work with blends of EP or EPDM polymers and propylene homopolymers (including isotactic polypropylene having more than 80% crystallinity) has demonstrated such blends to have moderate hot strength (i.e., cohesive strength and resistance to sagging or tearing during milling or other hot processing). Similar results were obtained by blending EP or EPDM polymers with many other components, (e.g., low density polyethylene, polyvinyl chloride, polybutylene, polystyrene, poly(ethylene/ethyl acrylate), poly(ethylene/vinyl acetate) and poly(ethylene/acrylic acid).
New polymer blends are desired having substantially improved hot strength.